A Very Modern Tube Headphone Amplifier

February 27, 2021 by Jenny List 34 Comments

Once a discarded relic, over the years the humble vacuum tube has been rehabilitated in the arena of specialist audio. There are plenty of tube amplifiers now being manufactured, with a popular choice being headphone amplifiers that use a tube as a gain stage followed by an op-amp as a buffer with a low impedance output. This forms the basis of [Ratti3]’s amplifier, but with the added interest of a battery supply and a Bluetooth connection.

The tube circuit is a very conventional anode follower using an EF95 pentode. This provides plenty of gain and of course that “valve sound” beloved of audio enthusiasts, but suffers from an output impedance too high to drive a set of headphones. An NE5532 steps in for the op-amp buffer role, making for a very simple circuit. Power comes from a set of four 18650 Lithium-Ion cells with associated charger and balance boards, while a little switching boost converter provides the 100 volt HT for the tubes.

We’ve visited this type of amplifier before with a similar but much more rough-around-the-edges Chinese version. That had some astonishingly cheap Chinese tubes, but if we’re seeking better components it’s interesting to know just who makes tubes these days.

PS2 Gets Integrated HDMI

February 17, 2021 by Tom Nardi 34 Comments

It might be difficult to imagine in our modern HDMI Utopia, but there was a time when game consoles required proprietary cables to connect up to your TV. We’re not just talking about early machines like the NES either, turn of the millennium consoles like the PlayStation 2, Gamecube, and the original Xbox all had weirdo A/V ports on the back that were useless without the proper adapter.

But thanks to the efforts of [Taylor Burley], you can now upgrade your Slim PS2 with integrated HDMI capability. It’s not even a terribly difficult modification, as these things go. Sure there’s a lot of soldering involved to run from the console’s A/V connector to the commercially-made HDMI dongle he’s hidden inside the case, but at least it’s straightforward work.

Tapping into the console’s A/V connector.

As [Taylor] shows in the video after the break, all you have to do is remove the proprietary connector from the HDMI adapter dongle, and wire it directly into the console’s A/V port with a bit of ribbon cable. There are only 8 pins in the connector that you need to worry about, and the spacing is generous enough that there’s no problem getting in there with your iron and some standard jumper wires. You’ve also got to pull 5 V from the board to power the adapter, but that’s easy enough thanks to the system’s nearby USB ports.

There’s a perfect spot to mount the adapter board next to the console’s Ethernet connector, and once that’s tacked down with a bit of adhesive, the only thing left to do is cut a hole in the back of the enclosure for the HDMI port and snip away a bit of the metal RF shield. Presumably the same modification could be done on the original “fat” PS2, though you’ll be on your own for finding a suitable place to mount the board.

While modern game consoles can easily emulate their earlier peers, providing enhanced graphical fidelity and introducing modern conveniences like wireless controllers in the process, there’s still something to be said for playing classic games on the original hardware. Even if these projects are fueled by little more than youthful nostalgia, it’s a safe bet we’ll continue to see folks keeping these older machines running far into the future.

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Restored Dreamcast Is A SEGA Fan’s Dream Come True

February 11, 2021 by Tom Nardi 43 Comments

[Bren Sutton] has been a long time fan of SEGA’s Dreamcast, eagerly snapping one up right around its October 1999 European release. But after years of neglect and a somewhat questionable paint job a decade or so back, he decided it was time to spruce his old friend up. He could have just cleaned the machine and been done with it, but he took the opportunity to revamp the console’s internals with both practical and cosmetic trickery.

The first step was getting the system looking a bit fresher. Removing the silver metallic paint he applied in his youth with a rattle can wasn’t going so well, so he ended up buying a broken donor console on eBay so he’d have a new shell to work with. The donor was yellowed with age, but a coating of peroxide cream and a few hours under a cheap UV light got it whitened up nicely. Now that he had a fresh new case, [Bren] turned his attention to the internal components.

Those who might be plugged into the active Dreamcast homebrew scene may already know that several upgrade modules exist for SEGA’s last home game console. One of the most popular replaces the optical drive with an SD card filled with your favorite game ISOs. You can also get a modern high efficiency power supply, as well as a board that replaces the original soldered-on clock battery with a slot that fits a CR2032. [Bren] threw them all in, ensuring several more years of gaming bliss.

But he wasn’t done yet. He also wanted to add some visual flair to his new and improved console. After some consideration, he gingerly cut the logo out of the Dreamcast’s lid, and installed an Adafruit CLUE board underneath it. With a few carefully crafted GIFs installed onto the CircuitPython-powered board, the console now has a gorgeous fully animated logo that you can see in the video after the break.

[Bren] could have really taken his console to the next level by doubling its available RAM to an eye-watering 32 MB, but considering the limited software support for that particularly bodacious modification, we’ll let it slide. Continue reading “Restored Dreamcast Is A SEGA Fan’s Dream Come True” →

GBA Gets Homebrew USB Charging Upgrade

February 6, 2021 by Tom Nardi 18 Comments

Sure there are pre-made kits to add a rechargeable battery and USB-C compatibility to Nintendo’s venerable Game Boy Advance, but [HorstBaerbel] thought he could throw together something similar for a fraction of the price. Plus, he wouldn’t have to wait on shipping. The end result might not be quite as polished, but it’s certainly impressive for what’s essentially a junk bin build.

The star of the show is the popular TP4056 lithium-ion charger module. [HorstBaerbel] went with the more common micro USB version, but these boards are also available with USB-C should you want to embrace the future. The module fits nicely inside the original battery compartment while while still leaving room for a 1,000 mAh pouch cell. The 4.2 V output of the fully charged battery is a bit too high for the Game Boy’s liking, so he used the forward voltage drop of a diode to bring it down to a more acceptable 3.5 V.

Naturally this does waste a good deal of energy, especially compared to the DC-DC converters used in commercial offerings like the CleanJuice, but it still delivers a respectable seven hours of runtime. The only issue with this modification seems to be that you’ve got just five minutes to save your progress and shut down when the GBA’s low-battery light goes on; but what’s life without a little excitement?

While not nearly extreme as some of the other GBA modifications we’ve seen over the years, this project is yet another example of the seemingly unlimited hacking potential of Nintendo’s iconic Game Boy line.

Civil Defense Disco Ball Rocks Ground Zero

January 15, 2021 by Tom Nardi 9 Comments

Old Civil Defense survey meters like the V-715 are interesting conversation starters, but of very little practical use today. These devices were intended to be a sort of litmus test that survivors of a nuclear blast could use to determine when it was safe to venture out of their radiation shelter: if the needle on the meter moves, even when it’s on the most sensitive setting, you should probably go back inside. Since [Hamilton Karl] would (hopefully) never need such an indicator, he decided to have a little fun with this Cold War holdover and turn it into a Disco Containment Unit.

Technical details are a little sparse on this one, but we can infer most of it just from the pictures. In place of the original meter [Hamilton] has mounted a tiny mirrored ball inside of a protective cage, which is spun by a geared motor that’s occupying the space that used to be taken up by the ion chamber.

A handful of Adafruit NeoPixel RGB LEDs, an Arduino Nano, and a few switches to control it all round out the functional aspects of the build, and a new disco-themed trefoil replaces the original Civil Defense logo on the side. The project page mentions there’s a piezo buzzer onboard that performs a stirring rendition of “Stayin’ Alive” by the Bee Gees, but alas there’s no video that shows it in action.

Thanks to the rugged construction and built-in handle of these old survey meters, [Hamilton] can now take the party with him wherever he goes. Not that he can really go anywhere with this whole global pandemic hanging over our heads, but at least he’ll be ready when things start trending towards normal. In a way the device’s functionality has now been reversed from how it originally worked, since the meter going wild will now be an indicator that its safe to come out.

While the V-715 isn’t of much use outside of a post-apocalyptic hellscape, the V-700 is actually a proper Geiger counter that’s still useful for surveying or research. An important distinction to remember if you ever get a chance to snap one of them up at a swap meet or flea market. Whenever we can start having those again, anyway.

It Isn’t Rocket Science — Wait, Maybe It Is

January 13, 2021 by Al Williams 22 Comments

We don’t know why, but for some reason, the more dangerous something is, the more hacker appeal it seems to have. We like to deal with high temperatures, high voltages, dangerous chemicals, and powerful lasers. So [Tech Ingredient’s] recent video about homemade rocket motors certainly caught our attention. You may need a little commitment, though. The first video (yes, there isn’t just one) is over an hour long.

Turns out, [Tech] doesn’t actually want to use the rockets for propulsion. He needed a source of highly-ionized high-velocity plasma to try to get more power from his magnetohydrodynamic project. Whatever you want to use it for, these are serious-sized motors. [Tech] claims that his design is both powerful and easy to build. He also has a “secret” rocket fuel that he shares. What is it? We won’t spoil the video for you, but it is a sweet surprise.

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Extremely Simple Tesla Coil With Only 3 Components

January 12, 2021 by Anool Mahidharia 22 Comments

Tesla Coils are a favourite here at Hackaday – just try searching through the archives, and see the number of results you get for all types of cool projects. [mircemk] adds to this list with his Extremely simple Tesla Coil with only 3 Components. But Be Warned — most Tesla coil designs can be dangerous and ought to be handled with care — and this one particularly so. It connects directly to the 220 V utility supply. If you touch any exposed, conductive part on the primary side, “Not only will it kill You, it will hurt the whole time you’re dying”. Making sure there is an ELCB in the supply line will ensure such an eventuality does not happen.

No prizes for guessing that the circuit is straight forward. It can be built with parts lying around the typical hacker den. Since the coil runs directly off 220 V, [mircemk] uses a pair of fluorescent lamp ballasts (chokes) to limit current flow. And if ballasts are hard to come by, you can use incandescent filament lamps instead. The function of the “spark gap” is done by either a modified door bell or a 220 V relay. This repeatedly charges the capacitor and connects it across the primary coil, setting up the resonant current flow between them. The rest of the parts are what you would expect to see in any Tesla coil. A high voltage rating capacitor and a few turns of heavy gauge copper wire form the primary LC oscillator tank circuit, while the secondary is about 1000 turns of thinner copper wire. Depending on the exact gauge of wires used, number of turns and the diameter of the coils, you may need to experiment with the value of the capacitor to obtain the most electrifying output.

If you have to look for one advantage of such a circuit, it’s that there is not much that can fail in terms of components, other than the doorbell / relay, making it a very robust, long lasting solution. If you’d rather build something less dangerous, do check out the huge collection of Tesla Coil projects that we have featured over the years.

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